Wireless power transfer can be used in a wide variety of applications directly power devices and/or recharge batteries. Two examples of wireless power transfer are magnetic induction and radio frequency (RF) energy transfer. Magnetic induction, which may also be referred to as inductive coupling, has a high transmission efficiency but usually for short distances. RF energy transfer, in contrast, has lower transmission efficiency but can work at longer distances.
A magnetic induction system can be designed for specific operating distances by, for example, selecting the sizes and shapes of the coils. By varying the system design, one magnetic system may have a good efficiency at a particular distance, such as less than one half of an inch, but performance may degrade significantly at longer distances. Another induction system may be configured to have better relative efficiency at a distance of, for example, several inches, but performance again will degrade at other ranges. As a result, magnetic induction systems are designed for a particular application with a fixed physical configuration. For example, a charging station may be configured to provide acceptable amounts of charging at the fixed distance that results from placing a toothbrush on the dedicated charging station. Placing the toothbrush even an inch away from the charging station though will not result in any charging.
Another drawback of magnetic inductive systems is that the transmitter coils and receiver coils must be both vertically and horizontally aligned. As a result, charging stations provide a physical holster that will hold the device to be charged in a particular configuration. Offsetting the device to be charged from the charging station even slightly results in rapid degradation of charging performance.
A device may be recharged using RF energy at much greater distances extending miles from the charging station, but the overall efficiency is usually lower.
Embodiments of the disclosed systems and methods overcome these and other problems.